The invention relates to wheel suspension and mounting assemblies for wheeled vehicles, and more particularly to a low-profile in-wheel suspension permitting a low aerodynamic drag installation, particularly suitable to light road vehicles and other wheeled vehicles.
Light road vehicles, such as electric vehicles, human powered vehicles, solar powered vehicles and the like, typically are required to utilize propulsive power in a highly efficient manner and to reduce aerodynamic drag to a high degree. In such cases, it is advantageous to mount a wheel on a streamlined assembly with a low overall frontal profile. Conventional automotive-type suspensions typically include a plurality of exposed struts, springs and other suspension components, each of which contributes to the overall aerodynamic drag. What is needed is a compact and streamlined suspension assembly with low frontal profile which absorbs and damps road impact and vibration, without a plurality of independently-exposed drag-producing components.
The wheel suspension of the invention relates to a thin-profile wheel suspension system including spring and dampening mechanisms and an optional braking mechanism. These wheel suspension components are mounted to a suspension frame in a compact arrangement which typically permits all or most of the moving (sprung) suspension components to be mounted within the volume enclosed by the rim of a wheel, i.e., within the internal volume defined by the concave surface formed by the wheel and rim. Due to this configuration, the compact low-profile wheel suspension of the invention may be referred to as an xe2x80x9cin-wheel suspensionxe2x80x9d.
The wheel suspension of the invention comprises a hub mounting assembly or hub plate assembly which comprises a hub/bearing assembly including an axle and preferably doubly clamped bearings. The bearings may be conventional ball bearings or tapered roller bearings. The hub/bearing assembly or hub plate may optionally include a brake mechanism, a drive motor or a power transmission mechanism.
The hub mounting assembly or hub plate is mounted and connected to a suspension frame by a motion-controlling inter-engaging sliding mount assembly, which connects the hub plate to the suspension frame while it permits the hub plate to slidably move in a controlled manner. The suspension frame is in turn typically mounted to a vehicle body or frame by conventional mounting means.
The inter-engaging sliding mount assembly connects to both the suspension frame and to the hub plate, and internally permits a sliding action in one direction or line of motion while maintaining a connection which is stable relative to motion in other directions or perpendicular to the permitted line of motion. The inter-engaging sliding mount assembly permits motion of the hub plate with one degree of freedom, e.g., vertical translation, while restraining motion of the hub plate in other degrees of freedom (e.g., laterally, front-to-rear and rotation).
Note that while the sliding motion permitted by the inter-engaging sliding mount assembly is typically in a straight line (e.g., along a straight guide rail or slot), the sliding mount assembly may permit sliding motion along a curved path (e.g., along a curved guide rail or slot). For purposes of this description, the terms xe2x80x9cdirectionxe2x80x9d or xe2x80x9cline of motionxe2x80x9d include sliding motion in a pre-selected curved path.
In the preferred embodiment, the sliding mount assembly comprises two pairs of slide-and-rail mechanisms aligned vertically on the suspension frame and mounted also to the hub plate. The suspension frame may be in the form of an fork-and-strut assembly in which two support forks extend spaced apart in parallel alignment vertically downward from a support strut. Each fork mounts one of the slide-and-rail mechanisms in parallel vertical alignment with each other. The hub plate attaches to the slide-and-rail mechanism on each side of the wheel hub, permitting vertical motion of the hub plate in the plane of the suspension forks.
In one embodiment, the slide-and-rail mechanism includes a rail mounted to each fork, each rail engaging one or more sliding rail mounts or sliders which wholly or partially surround the rail. The sliders attach to and support the hub plate. The rails and the sliders thus form a slidable connection between the wheel/ hub plate and the fixed suspension fork thereby holding the wheel securely in place. The sliding rails/rail mount linkage allows limited up and down movement of the wheel along the sliding rails in response to road shock. The sliding rails may be made of metal, an alloy or a polymer and/or comprise linear bearings.
A spring mechanism is mounted extending between and connecting to both the hub plate and the suspension frame or fork to provide resilient elastic motion control of the hub plate relative to the suspension frame in response to vehicle weight, vehicle motion and road shock. The spring mechanism preferably includes a damping device to dampen the movement of the hub plate and wheel, e.g., due to uneven road surfaces or terrain.
The preferred spring mechanism is at least one conventional piston-type shock absorber including both a spring and a fluid-flow damper in an integrated, elongate unit having mounting fittings at each end. Alternative spring mechanisms may be employed, such as coil springs, leaf springs, elastic cords or bungees, rubber compression springs and the like. Alternative damping devices may be included, such as frictional dampers and the like.
In the preferred embodiment, the shock absorber is mounted between the sliding hub mount and the fixed suspension fork in generally parallel alignment to the rails, using conventional fasteners and brackets to attach the mount fittings of the shock absorber to the fork and hub plate respectively. The lower part of the shock absorber is attached to the hub plate and the upper part is secured to the fixed suspension fork. In the preferred embodiment, the upper attachment is adjacent the base of the strut portion and the lower attachment is adjacent the bottom of the hub plate, to one side of the bearing and axle, to provide a compact arrangement.
A braking mechanism may be attached to the hub plate. Various alternative conventional types of brakes may be used, such as hub mounted disk brakes, drum brakes, bicycle-type caliper brakes, and the like. The preferred embodiment eliminates the need for a separate brake drum by mounting an opposed pair of brake pads and actuators, disposed to press outwardly from the hub assembly to bear upon the inner surface of the wheel rim.
The suspension of the invention allows for high ground clearance and low unsprung weight which reduces energy losses when the vehicle is in motion. The narrow frontal profile of the in-wheel suspension also improves the aerodynamic characteristics of the vehicle. Another advantage of this suspension design is the versatility of the in-wheel suspension which allows the vehicle to be driven on regular surface roads such as asphalt, concrete, etc. as well as dirt roads and in rugged terrain. One or multiple shock absorbers may be used. The shock absorbers may be of the air or oil-filled type, the coil-type, or be made of elastomer products. They are adapted to fit into the in-wheel suspension system.
The dampening effect of the shock absorber(s) along the sliding rails may be controlled electronically by a linear motor. The linear motor may be used to control the stiffness of the suspension, or it may be used to produce electricity like a generator. In another alternative embodiment, the hub assembly may include an in-wheel motor to allow for direct drive of the wheel from the electric motor.
In addition to controlling the dampening effect, the shock absorber or other spring mechanism can be adjusted to control the linear positioning, along the rails, of a fixed location on the slidable hub mount assembly relative to a fixed location on the suspension frame. Thus, not only can the suspension""s dynamic response be controlled, but also the overall physical orientation of the device incorporating the invention. By way of example, when the preferred embodiment is employed on a wheeled vehicle, said vehicle""s height above and angle with respect to the ground can be controlled.